Smokeable sausage casing based on polyamide

ABSTRACT

The invention relates to smokeable sausage casings which are based on polyamide and polymers containing polyamide blocks and polyether blocks. The said smokeable, heat-shrinkable tubular sausage casings are particularly suitable for the manufacture of cooked meat sausages, scalded-emulsion sausages, cooked or rapidly fermented sausages containing fat and smoked ham. The smokeable sausage casing comprises 15-85 wt % of a polyamide (i) or a combination of polyamides (i) and 15-85 wt % of a polymer (ii) containing polyamide blocks and polyether blocks or a combination of polymers (ii).

[0001] The invention relates to smokeable sausage casings which arebased on polyamide and polymers containing polyamide blocks andpolyether blocks. The said smoke-able, heat-shrinkable tubular sausagecasings are particularly suitable for the manufacture of cooked meatsausages, scalded-emulsion sausages, fat-containing cooked or fermentedsausages and smoked ham.

[0002] Cooked meat sausages are conventionally manufactured using edibleor non-edible collagen casings, natural casings formed from naturalmaterials like animal intestines, fibrous or cellulose casings ororiented or unoriented plastic casings comprising one or several layers.Smoke penetrates fibrous casings and cellulose casings and thus they arewidely used in the manufacture of cooked meat sausages. However, themanufacturing process for fibrous casings and cellulose casings involvesthe use of the viscous process which causes undesirable emissions ofcarbon disulphide and hydrogen sulphide to the atmosphere. This is amajor environmental problem and unacceptable nowadays in many countries.Fibrous casings manufactured from regenerated cellulose are oftendifficult to peel from sausages without braking the casing. Because ofthe high permeability of fibrous casings significant weight loss ofsausages takes place during the manufacture and especially during thecooling process.

[0003] Cooked or fermented sausages containing substantial amounts offat are manufactured in cellophane casings and in fibrous casings, whichare easily smokeable. However, fat tends to leak out through the casingand clips or seams thus making the appearance and handling of suchsausages unclean. Also such sausages may develop black spots on thecasing, caused probably by sulphur compounds in the casing, resulting inthat such sausages cannot be sold to consumers.

[0004] In the manufacturing process sausage casings are usually soakedbefore filling with sausage mix and mould-preventing agents are requiredto prevent potential growth of moulds in the humid casings. All ofnatural casings and most of synthetic casings according to the state ofthe art are not heat-sealable and thus clips or other sealing means haveto be used.

[0005] There is also a potential risk of BSE when using sausage casingformed from natural materials like bovine intestines and thus they arenot so popular any more as sausage casings. Plastic casings aregenerally regarded as casings which are not smokeable because they arepoorly or not at all smoke permeable and thus they are not suitable forthe manufacture of sausages which are smoked.

[0006] Several plastic films for packaging of food products are knownand these films are usually based on poly(ethylene terephthalate) (PET),poly(vinylidene chloride) (PVDC) and polyamide (PA), also known asnylon. Axially stretched PET casings are usually not suitable for cookedmeat sausages or scalded-emulsion sausages because they are poorlyextendable and they shrink only very little.

[0007] PVDC casings are more extensible but, however, they are morelikely to loose their shape after filling. Special equipment is requiredfor the extrusion of PVDC, and because chlorine containing PVDC casingsare brittle, they usually contain as plasticizers phthalates which areconsidered potentially hazardous substances to health. Additionally, asPVDC casings contain chlorine, their disposal is problematic and in manycountries the use of PVDC in food packaging is forbidden nowadays.

[0008] Polyamide casings are more extensible, they shrink to a greaterextent and they are more suitable for cooked meat sausages, however theyare not considered smokeable. Several polyamide based sausage casingsare known in the art, single-layer sausage casings and also multi-layercasings. U.S. Pat. No. 5,773,059 discloses a polyamide based sausagecasing of a polymer blend which comprises:

[0009] a) polyamide 6 (nylon 6),

[0010] b) 5-50 wt %, based on the total weight of all polymers in thelayer of

[0011] b1) aliphatic copolyamide containing units of the formulae—NH—(CH₂)₅—CO and —NH—(CH₂)_(m)—CO, where m is an integer from 7-11, or

[0012] b2) an aliphatic copolyamide containing units of the formulae—NH—(CH₂)₅—CO—, —NH—(CH₂)_(n)—NH— and —CO—(CH₂)_(o)—CO where n is aninteger from 6-12 and o is an integer from 7-10, or both b1) and b2),and

[0013] c) 0-20 wt % of an amorphous copolyamide containing hexamethylenediamine, and at least one of terephthalic acid and isophathalic acidunits, and

[0014] d) 0-20 wt % of a polyolefin modified by carboxylic groups.

[0015] This casing is a blend of polyamides and it may optionallycontain a coextruded polyolefin layer. Polyolefin casings are generallynot regarded as smokeable. The casings according to this publication areparticularly suitable for the manufacture of scalded-emulsions sausagesand cooked meat sausages by mechanical and especially by manual filling,but they have poor smoke permeability.

[0016] EP 476,963 discloses films composed of a mixture (i) of acopolymer with polyamide blocks and polyether blocks which arehydrophilic, (ii) of a hydrophobic polymer which can be the precedingcopolymer but with hydrophobic polyether blocks or a polyamide or apolyurethane, and (iii) optionally of a compatibilizing agent. The filmis permeable to water vapour and impermeable to liquid water and has alow water uptake.

[0017] EP 0797918 is concerned with a smokeable casing comprisingpolyamide and polyolefin. The casings according to this publicationcomprises a heat-shrinkable tubular laminate including at least onelayer of a polyamide resin and at least one layer of a modifiedpolyolefin resin. Said casings require very long smoking processes whichare not suitable for example for cooked meat sausages on an industrialscale.

[0018] WO 98/19551 discloses polyamide-based sausage skins which can befilled manually without or with minor filling pressure and they aresuitable for cooked sausages. Said sausage skins are biaxially strechedand thermofixed, tubular seamless casings with one or more layers,wherein at least one of the layers comprise a block copolymer accordingto any of the following formulas (I)-(III), with hard aliphaticpolyamideblocks and soft aliphatic polyether blocks:

E_(a)-(NH—[CH₂]_(x)—CO)_(m)—X_(a)-(A-O)_(n)-A-X_(a)—(CO—[CH₂]_(x)—NH)_(m)-E_(a)  (I)

[0019] wherein A is an alkanediyl residue of formula —CH₂—CH₂—(=ethane-1,2-diyl),

[0020] —CH₂—CH(CH₃)— (=propane-1,2-diyl) or

[0021] —(CH₂)₄— (=butane-1,4-diyl),

[0022] X_(a) is O— or —NH—,

[0023] E_(a) is H, (C₂-C₈) allanoyl, benzoyl or phenylacetyl,

[0024] —CO—N([CH₂]_(x−1)—CH₃)—CO—(C₁-C₄) alkyl,

[0025] —CO—N([CH₂]_(x−1)—CH₃)—CO—C₆H₅ or

[0026] —CO—N([CH₂]_(x−1)—CH₃)—CO—CH₂—C₆H₅,

[0027] x is an integer from 5 to 11, m is an integer from 30 to 200 andn is an integer from 4 to 60,

[0028] wherein X_(b) is an alkanediyl residue of formula —[CH₂]_(z)—,

[0029] where z is an integer from 4 to 10,

[0030] meta- or para-phenylene,

[0031] —NH—(C₁-C₆) alkyl-NH—,

[0032] —NH—C₆H₃—(CH₃)—NH—

[0033] >N—[CH₂]_(x−1)—CH₃, —[CH₂]_(z)—CO—N([CH₂]_(x−1)—CH₃ )— or

[0034] —C₆H₄—CO—N([CH₂]_(x−1)—CH₃)—, where C₆H₄ represents meta- orpara-phenylene

[0035] E_(b) is —OH, —O—(C₁-C₇) alkyl, —O-phenyl or

[0036] and

[0037] A, m and n have the above meanings;

—[X—(CO—[CH₂]_(x)—NH)₀—Y—X—(A-O)_(p)-A]-   (III)

[0038] wherein Y is —CO—, —CO—[CH₂]_(z)—CO—, —CO—C₆H₄—CO— or

[0039] where C₆ H₄ represents meta- or para-phenylene, or

[0040] —CO—N([CH₂]_(x−1)—CH₃)—CO—,

[0041] —CO—N([CH₂]_(x−1)—CH₃)—CO—[CH₂]_(z)—CO—N([CH₂]_(x−1)—CH₃)—CO—,

[0042] —CO—N([CH₂]_(x−1)—CH₃)—CO—C₆H₄—CO—N([CH₂]_(x−1)—CH₃)—CO—,

[0043] where C₆H₄ has the given meaning, o is an integer from 10 to 150,p is an integer from 4 to 100 and A, x and z have the above givenmeanings.

[0044] These sausage skins are not designed for smoked sausages as thethickness of the casings is high and polymers of hydrophobic nature areused. Additionally, the moisture vapour transmission rate of saidsausage skins is very low.

[0045] Traditionally, only sausages manufactured into collagen casings,cellulose casings or fibrous casings of regenerated cellulose orsausages manufactured in casings made from other natural materials aresmokeable. Plastic casings are generally not used for sausages which aresmoked as they are not considered smokeable. Based on the above it canbe seen that there exists a need for smokeable sausage casings for themanufacture of cooked meat sausages, scalded-emulsion sausages,fat-containing cooked or fermented sausages and smoked ham, whichmanufacture takes place particularly on an industrial scale.

[0046] An object of the present invention is to provide a smokeablesausage casing for cooked meat sausages, scalded-emulsion sausages,fat-containing cooked or fermented sausages and smoked ham. Anotherobject of the invention is to provide a method for the manufacture ofcooked meat sausages, scalded-emulsion sausages, fat-containing cookedor fermented sausages and smoked ham, in smokeable sausage casings.

[0047] The characteristic features of the smokeable sausage casings forcooked meat sausages, scalded-emulsion sausages, fat-containing cookedor fermented sausages and smoked ham and of the method for themanufacture of cooked meat sausages, scalded-emulsion sausages,fat-containing cooked or fermented sausages and smoked ham are providedin the claims.

[0048] Surprisingly it has been found that the disadvantages andproblems related to the casings and manufacturing methods according tothe state of the art can be avoided or at least significantly decreasedwith the smokeable casing according to the invention. Said smokeablesausage casings can be manufactured from a specific combination of atleast one polyamide (i) and at least one polymer (ii) containingpolyamide blocks and polyether blocks. It has been noticed that thesmokeability of the casing is directly proportional to the moisturevapour transmission rate (MVTR) of the casing.

[0049] Suitable polyamides (i) are selected from the group comprising:

[0050] PA6=H—(NH—(CH₂)₅—CO)_(n)—OH (nylon-6), homopolymer or copolymer,

[0051] PA66=H—(NH—(CH₂)₆—HN—CO—(CH₂)₄—CO)_(n)—OH (nylon 66),

[0052] PA6.12=H—(NH—(CH₂)₆—HN—CO—(CH₂)₁₀—CO)_(n)—OH (nylon 612),

[0053] PA6/66=H—(NH—(CH₂)₅—CO)—OH+H—(NH—(CH₂)₆—HN—CO—(CH₂)₄—CO)—OH (inrandom order) (nylon6/66),

[0054] PA6/12=H—NH—(CH₂)₅—CO)—OH+H—(NH—(CH₂)₁₁—CO)—OH (in random order)(nylon 6/12),

[0055] PA6/69=H—(NH—(CH₂)₅—CO)—OH+H—(NH—(CH₂)₆—HN—CO—(CH₂)₇—CO)—OH (inrandom order) (nylon 6/69), and

[0056] MXDA containing polyamides, partially aromatic polyamides andmixtures of above mentioned polyamides.

[0057] Preferable ones are PA 6/66, PA6 or mixtures of PA 6/66 and PA6.

[0058] Suitable polymers (ii) containing polyamide blocks and polyetherblocks are selected from the group comprising thermoplastic polymershaving polyether chains and it being possible for these chains to beside chains (copolymer B) or to be blocks (or sequences) in the mainchain (copolymer A) or to be present as side chains or as blocks.

[0059] Mention may be made, as an example of a polymer having polyetherside chains, of copolymers of ethylene and of a polyalkylene glycol(meth)acrylate, such as those disclosed in EP 848,019, the contents ofwhich are incorporated in the present application.

[0060] Mention may be made, as an example of a polymer A havingpolyether blocks, of the copolymer (A) of WO 98/26004 which means ablock copolymer in which polyoxyalkylene chains and other polymer chainsare linked together, or a polymer in which polyoxyalkylene chains areconnected together via coupling regions.

[0061] The polyether blocks comprise alkylene oxide units which can bechosen from ethylene oxide, propylene oxide and —CH₂—CH₂—CH₂—CH₂—O—. Thewater vapour permeability increases with the proportion of polyether andwith its nature. The greater the amount of polyethylene glycol, thegreater the permeability to water vapour.

[0062] The polyether blocks can represent 5 to 85% by weight of (A). Thepolyether blocks can comprise other units than ethylene oxide units,such as, for example, propylene oxide or polytetrahydrofuran, whichresults in polytetramethylene glycol linkages. It is also possiblesimultaneously to use PEG blocks, that is to say those composed ofethylene oxide units, PPG blocks, that is to say those composed ofpropylene oxide units, and PTMG blocks, that is to say those composed oftetramethylene glycol units, also known as polytetrahydrofuran blocks(PTHF). Use is preferably made of PEG blocks or of blocks obtained byoxyethylation of bisphenols, such as, for example, bisphenol A. Thelatter products are disclosed in EP 613,919.

[0063] Polyether blocks comprised different units, such as units derivedfrom ethylene glycol (—OC₂H₄—), from propylene glycol

[0064] or from tetramethylene glycol (—O—(CH₂)₄—) are also suitableones.

[0065] The amount of polyether blocks in (A) is preferably from 10 to50% by weight of (B). Advantageously, (A) is a copolymer with polyamideblocks and polyether blocks.

[0066] Polymers with polyamide blocks and polyether blocks result fromthe copolycondensation of polyamide sequences comprising reactive endswith polyether sequences comprising reactive ends, such as, inter alia:

[0067] 1) polyamide sequences comprising diamine chain ends withpolyoxyalkylene sequences comprising dicarboxylic chain ends,

[0068] 2) polyamide sequences comprising dicarboxylic chain ends withpolyoxyalkylene sequences comprising diamine chain ends obtained bycyanoethylation and hydrogenation of α,ω-dihydioxylated aliphaticpolyoxyalkylene sequences, known as polyetherdiols,

[0069] 3) polyamide sequences comprising dicarboxylic chain ends withpolyetherdiols, the products obtained being, in this specific case,polyetheresteramides.

[0070] Polyamide sequences comprising dicarboxylic chain ends originate,for example, from the condensation of α,ω-aminocarboxylic acids, oflactams or of dicarboxylic acids and diamines in the presence of achain-limiting dicarboxylic acid. The polyamide blocks are made ofpolyamide-6 or polyamide-12 and preferably of polyamide-6.

[0071] The number-average molar mass of the polyamide sequences isbetween 300 and 15,000 and preferably between 600 and 5000. The mass ofthe polyether sequences is between 100 and 6000 and preferably between200 and 3000.

[0072] The polyamide blocks and polyether blocks can also compriserandomly distributed units. These polymers can be prepared by thesimultaneous reaction of the polyether and of the precursors of thepolyamide blocks.

[0073] For example, polyetherdiol, a lactam (or an α,ω-amino acid) and achain-limiting diacid can be reacted in the presence of a small amountof water. A polymer is obtained which has essentially polyether blocksand polyamide blocks of very variable length but also the variousreactants which have reacted randomly, which are statisticallydistributed along the polymer chain.

[0074] These polymers with polyamide blocks and polyether blocks,whether they originate from the copolycondensation of polyamide andpolyether sequences prepared beforehand or from a one-stage reaction,exhibit, for example, Shore D hardnesses which can be between 20 and 75and advantageously between 30 and 70 and an intrinsic viscosity between0.8 and 2.5, measured in meta-cresol at 25° C. for a startingconcentration of 0.8 g/100 ml.

[0075] Whether the polyether blocks derive from polyethylene glycol,polypropylene glycol or polytetramethylene glycol, they are either usedas is and copolycondensed with polyamide blocks comprising carboxylicends or they are aminated, in order to be converted intopolyetherdiamines, and condensed with polyamide blocks comprisingcarboxylic ends. They can also be mixed with polyamide precursors and achain-limiting agent in order to form polymers with polyamide blocks andpolyether blocks having statistically distributed units.

[0076] The polyether is preferably polyethylene glycol (PEG).

[0077] Whether the polyether blocks are in the chain of the polymer withpolyamide blocks and polyether blocks in the form of diols or ofdiamines, they are known for simplicity as PEG blocks.

[0078] The polymer (ii) with polyamide blocks and polyether blockspreferably comprises a single type of polyamide block and a single typeof polyether block. Use is made of polymers with PEG blocks having agreater permeability to water vapour.

[0079] The polymer with polyamide blocks and polyether blocks isadvantageously such that the polyamide is the major constituent byweight, that is to say that the amount of polyamide which is in the formof blocks and that which is optionally statistically distributed in thechain represents 40% by weight or more of the polymer with polyamideblocks and polyether blocks. The amount of polyamide and the amount ofpolyether are advantageously in the ratio (polyamide/polyether) 1/1 to3/1.

[0080] A suitable polymer (ii) is a hydrophilic polymer having polyetherchains and with a moisture vapour transmission rate (MVTR) of more than100 g /m²/24 hours, preferably 250-20.000 g/m²/24 hours when measuredusing the ASTM E96 BW method. Also combinations of such polymers (ii)may be used.

[0081] The smokeable sausage casing according to the invention comprises15-85 wt %, preferably 50-70 wt % of the polyamide (i) or a combinationof polyamides (i) and 15-85 wt %, preferably 30-50 wt % of thehydrophilic polymer (ii) with polyamide blocks and polyether blocks,preferably polyethylene glycol (PEG) blocks, or a combination ofhydrophilic polymers (ii) with polyamide blocks and polyether blocks.Preferably the smokeable sausage casing comprises a polyamide (i)selected from PA6, PA6/66 and mixtures thereof and a polymer (ii) withpolyamide PA6 blocks and polyether PEG blocks, which polymer (ii) has amoisture vapour transmission rate (NIVTR) of more than 100 g /m²/24hours, preferably 250-20.000 g/m²/24 hours (ASTM E96 BW). The obtainedsausage casing is preferably biaxially stretch-oriented and it has amoisture vapour transmission rate (MVTR) of more than 200 g /m²/24hours, preferably more than 400 g/M²/24 hours when measured using theASTM E96 BW method. The ratio of orientation is then 6-12, preferably7-9 (transverse orientation×lenght).

[0082] Polyamide (i) and polymer (ii) are mixed and converted into ahomogeneous melt which is extruded through a ring die and formed into aseamless tube which is then stretched in longitudinal and transversedirections i.e. biaxially stretch-oriented. Mixing and melting can beperformed in separate mixing extruders. The casing comprises one or morecoextruded layers which may comprise same or different polymers.

[0083] The manufacturing process of the sausage casings according to theinvention is simple and it presents no environmental problems related toemissions of volatile organic compounds or undesirable odours. Thepolymer leftovers from the manufacturing process can be recycled to theprocess and practically no waste is formed. Cooked meat sausages,scalded-emulsion sausages and fat-containing cooked or rapidly fermentedsausages requiring smokeability can easily be manufactured into thecasings according to the invention. The smoking may be performed usingnatural smoke or liquid smoke. The casing can be biaxiallystretch-oriented or unoriented with one or more layers, preferably it isbiaxially stretch-oriented. It may be in a tubular form which issealable with metal clips or other known method or it can beheat-sealed, or it can be in flat film that is sealable to a desiredfrom.

[0084] In the manufacturing process sausage mix or ham is stuffed intothe casings and the sausages or ham are smoked and cooked using aprogram characteristic to smoked sausages or smoked ham. The smokingprocess may be a hot smoke process and natural smoke or liquid smoke maybe used.

[0085] The finished sausage casing shows a shrinkage of 5-25% in crossdirection and of 5-25% in length direction in water at 78° C. Athickness of the stretched and thermoset sausage casing is 10-70 μm andpreferably 15-45 μm. The pressure resistance of the casing according tothe invention, with a thickness of 15 μm is more than 40 kPa. Thesausage casing according to the invention is preferably biaxiallystrechoriented and thermoset, it also may be shirred and it is peelableby machines. The casing requires no soaking step before stuffing and nomold pre-venting agents are needed. Anti-block agents and slip agentsknown in the art may be used if desired.

[0086] The obtained casing is suprisingly rapidly smokeable and thesmoked product has to taste and appearance like a sausage manufacturedin conventional smokeable casings. The required smoking time is shortthus making said sausage casings particularly suitable for themanufacture of cooked meat sausages, scalded-emulsion meat products andcooked or rapidly fermented sausages containing fat, on an industrialscale. Very thin casings can be manufactured still retaining goodpressure resistance, dimension stability and good cooking durability.Further, weight loss of sausages manufactured in casings according tothe invention is significantly lower than the one when using natural orcellulose based casings.

[0087] As the casings according to the invention are also heat-sealable,the manufacture of said sausages is more simple and economic. They arefat proof, no fat leaks through the casings which makes themparticularly suitable for a lot of fat-containing cooked or fermentedsausages and further, no black spots are formed on the casing.

[0088] The invention is further illustrated in the following withexamples to which the scope of invention is not limited.

EXAMPLE 1 Smokeability-Properties of Three Different Plastic Casings

[0089] Both smoke flavour and colour are formed by combined effect ofmany agents/substances and by their reactions with the product itself.Smoke flavour and colour do not necessarily form by influence of thesame factors, and besides certain factors have also synergisticproperties.

[0090] Smoking provides the following—conceived as positive—effects:flavouring, colouring, preserving by antioxidative and antimicrobialaction and formation of a secondary skin. (Tóth, L. & Potthast, K. 1984.Chemical aspects of the smoking of meat and meat products. In: “Advancesin Food Research, vol. 29”. Academic Press, Inc, Orlando, Fla. 1984.87-150.) Curing smoke consists of a dispersed phase of solid and liquidparticles as well as a gaseous phase. The size of liquid particlesvaries between 0.2-0.4 μm. (Bøgh-Sørensen, L., Højmark Jensen, J., Jul,M. 1981. Konserveringsteknik 2. Dsr Forlag, Kobenhavn.)

[0091] Here smokeability means the smoke-permeability properties of thecasing and term smokyness aroma, smoky taste and color of the final,peeled product. The smokeability-properties of three different plasticcasings according to the invention were compared with a nylon casing andcellophane casing.

[0092] Samples

[0093] 3 different plastic casings were examined. As reference samples acommercial nylon casing (Grilon F 47) and a commercial cellophane casingwere used. Compositions of the casings used are provided in thefollowing Table 1: TABLE 1 Casing nr Polyamide (i)/wt % Polymer (ii)/wt% 3 Grilon CR 9 HV/75% Pebax MH 1657/25% (nylon 6.12) (PA blocks + PEGblocks) 10 Ultramid C 4/70% Pebax MH 1657/30% (nylon 6/66) 11 Ultramid C4/70% Pebax MV 1074/30% (nylon 6/66) (PA blocks + PEG blocks)

[0094] Processing of the Sausages

[0095] Four plastic films (commercial nylon casing and casings 3, 10 and11) were extruded in tubular form and biaxially oriented to a totalorientation ratio of 9.0 and thermoset. The diameter of the thermosettubular casing was 22 mm and the thickness of the nylon casing was 20μm, and of casings 3, 10 and 11 16 μm. The sausage mix was stuffed intothe casings and the sausages were smoked and cooked by the programcharacteristic to smoked sausages. The smoking process was a hot smokeprocessing (50-85° C.) (Tóth & Potthast, 1984). After the cooking andcooling the sausages were vacuum-packed and cold-storaged at 3.5° C.

[0096] Methods of Analysis

[0097] Sensory Evaluation

[0098] The sensory evaluation of the products was carried out after twoand after three days from processing. The panel evaluated smokyness(smoke's intensity of aroma, taste and colour) from the peeled sausages.The sausages were peeled for the evaluation and cut into pieces. Thetemperature of the samples was about 20° C. and they were served inrandom order (coded) to the evaluators.

[0099] The evaluation method used was a graphic method (estimation ofintensity), in which the evaluators marked their opinion of theproduct's intensity of smoky aroma or taste or color on the 150 mm linesegment. The line segment was anchored from it's ends by the terms thatdescribed the studied property (aroma: no smoky aroma—intense smokyaroma; taste: no smoky taste—intense smoky taste; color: light—dark).

[0100] There were individual samples for aroma, taste and colourevaluation. The evaluations of aroma and taste were accomplished in redlight in order to prevent possible color differences between separatesamples to affect the evaluation.

[0101] Differences between the samples were examined by the analysis ofvariance (LSD-method). Correlation between individual factors wasexamined.

[0102] Results

[0103] The results of differences between samples (casings) regardingthe properties were examined and average values were calculated andshown in Table 2. TABLE 2 The results of sensory evaluation. The averagevalues given for samples; two evaluation times. Average value SampleNylon 10 11 3 Cellophane Aroma 24.5 52.8 60.3 52.9 101.0 Taste 21.0 47.666.3 50.8 92.4 Colour 17.5 75.7 63.6 49.3 119.1

[0104] The results show that the casings examined were significantlymore smoke-permeable than nylon casing and they fulfilled wellrequirements set for a smokeable casing

EXAMPLE 2 Industrial Manufacturing Process for Cooked Sausages

[0105] Standard cooked sausages stuffed in a casing with a thickness of30 μm and containing 70 wt % of Ube PA 5034 FDX 33 (PA 6/66) and 30 wt %of Pebax MH 1657 (PA6+PEG) were cooked and smoked according to followingprograms A and B which are suitable for the manufacture of sausages onan industrial scale. Program A/Slightly smoked cooked sausageTemperature/ Relative Time/ Test ° C. Humidity/% min Step 1. 60  98 10Formation of colour 2. 67  0  6 Drying 3. 70  45  2 Smoking 4. 72 100 20Cooking 5. 77 100  38* Cooking

[0106] Program B/Cooked sausage with a clear “smoked” aroma Temperature/Relative Time/ Test ° C. Humidity/% min Step 1. 60  98 10 Formation ofcolour 2. 65  0  8 Drying 3. 68  60  6 Smoking 4. 72 100 20 Cooking 5.77 100  33* Cooking

[0107] No changes in the weight of sausages tested in programs A or Bwere noticed. Suitable relative humidity during the smoking step variedbetween 45-60% when short smoking times of 2-6 min were used. Clearformation of desired colour could be noticed and the aroma and tastewere acceptable.

1. A smokeable sausage casing, characterized in that the casing isbiaxially strechoriented and it comprises 15-85 wt % of a polyamide (i)selected from the group comprising: PA6=H—(NH—(CH₂)₅—CO)_(n)—OH,homopolymer or copolymer, PA6.12=H—(NH—(CH₂)₆—HN—CO—(CH₂)₁₀—CO)_(n)—OH,and Pa6/66=H—(NH—(CH₂)₅—CO)—OH+H—(NH—(CH₂)₆—HN—CO—(CH₂)₄—CO)—OH (inrandom order), or a combination of polyamides (i); 15-85 wt % of ahydrophilic polymer (ii) containing polyamide pa6 blocks andpolyethyleneglycol (PEG) blocks or a combination of hydrophilic polymers(ii), the casing has a moisture vapour transmission rate (MVTR) of morethan 200 g/m²/24 hours when measured using the ASTM E96 BW method, andthe thickness of the casing is 15-45 μm.
 2. The smokeable sausage casingaccording the claim 1, characterized in that the casing comprises 50-70wt % of a polyamide (i) or a combination of polyamides (i) and 30-50 wt% of a hydrophilic polymer (ii) or a combination of hydrophilic polymers(ii).
 3. The smokeable sausage casing according to claim 1 or 2,characterized in that the hydrophilic polymer (ii) has a moisture vapourtransmission rate (MVTR) of more than 100 g/m²/24 hours, preferably250-20.000 g/m²/24 hours.
 4. The smokeable sausage casing according toany one of claims 1-3, characterized in that the casing has a moisturevapour transmission rate (MVTR) of more than 400 g/m²/24 hours.
 5. Thesmokeable sausage casing according to any one of claims 1-4,characterized in that the casing comprises one ore more layers and it isheat-sealable.
 6. The smokeable sausage casing according to any one ofclaims 1-5, characterized in that the casing is smokeable using naturalsmoke or liquid smoke.
 7. The smokeable sausage casing according to anyone of claims 1-6, characterized in that the finished sausage casingshows a shrinkage of 5-25% in cross direction and of 5-25% in lengthdirection in water at 78° C.
 8. Use of the smokeable sausage casingaccording to any one of claims 1-7 in the manufacture of cooked meatsausages, scalded-emulsion sausages, cooked or fermented sausagescontaining fat and smoked ham.
 9. A method for the manufacture of cookedmeat sausages. scalded-emulsion sausages, cooked or fermented sausagescontaining fat and smoked ham in smokeable sausage casings whereinsausage mix or ham is stuffed into a casings and the sausages or ham aresmoked and cooked. characterized in that the casing is biaxiallystrechoriented and it comprises 15-85 wt % of a polyamide (i) selectedfrom the group comprising: PA6=H—(NH—(CH₂)₅—CO)_(n)—OH, homopolymer orcopolymer, PA6.12=H—(NH—(CH₂)₆—HN—CO—(CH₂)₁₀—CO)_(n)—OH, andPA6/66=H—(NH—(CH₂)₅—CO)—OH+H—(NH—(CH₂)₆—HN—CO—(CH₂)₄—CO)—OH (in randomorder), or a combination of polyamides (i); 15-85 wt % of a hydrophilicpolymer (ii) containing polyamide PA6 blocks and polyethyleneglycol(PEG) blocks or a combination of hydrophilic polymers (ii), the casinghas a moisture vapour transmission rate (MVTR) of more than 200 g/m²/24hours when measured using the ASTM E96 BW method, and the thickness ofthe casing is 15-45 μm.
 10. The method according to claim 9,characterized in that the casing comprises 50-70 wt % of a polyamide (i)or a combination of polyamides (i) and 30-50 w % of a hydrophilicpolymer (ii) or a combination of hydrophilic polymers (ii).
 11. Themethod according to claim 9 or 10, characterized in that the hydrophilicpolymer (ii) has a moisture vapour transmission rate (MVTR) of more than100 g/m²/24 hours, preferably 250-20.000 g/m²/24 hours.
 12. The methodaccording to any one of claims 9-11, characterized in that the casinghas a moisture vapour transmission rate (MVTR) of more than 400 g/m²/24hours.
 13. The method according to any one of claims 9-12, characterizedin that the casing comprises one ore more layers and it isheat-sealable.
 14. The method according to any one of claims 9-13,characterized in that natural smoke or liquid smoke is used in smoking.15. The method according to any one of claims 9-14, characterized inthat the finished sausage casing shows a shrinkage of 5-25% in crossdirection and of 5-25% in length direction in water at 78° C.